This invention, though extensible to a broader spectrum of applications, was motivated by the development of a roadable aircraft. One of the challenges of developing a practical roadable aircraft is how to safely and securely stow the wings while operating in the road environment. Conveniently stowing a roadable or non-roadable aircraft's wings for storage could be accomplished with the same or similar techniques. This invention represents an improved method for accomplishing this.
A common method for stowing the wings of a roadable aircraft described in prior art is to rotate the wings into an orientation parallel to the fuselage of the aircraft. This is the approach taken in broad terms by Geisse (U.S. Pat. No. 2,424,068), Spitzer (U.S. Pat. No. 6,082,665), Pellarini (U.S. Pat. No. 2,674,422), Pham (U.S. Pat. No. 5,984,228), and Bragg (U.S. Pat. No. 6,086,014), among others. Some of the prior art does combine a fold with this rotation. The bi-fold invention described here improves upon this technique by reducing the side area of the vehicle on the road, thus improving safety in high-wind conditions; and by protecting more of the flight surface against potential damage from road debris. Additionally, a bi-folding wing can have a greater span while still allowing the roadable configuration of the aircraft to fit in a standard automotive parking space.
The bi-fold invention described here has many of the same advantages over the single fold wing designs common in naval military aircraft, such as the invention of Naumann (U.S. Pat. No. 2,712,421). A prior bi-fold wing design has been proposed by Schertz (U.S. Pat. No. 3,371,886) in which the wing hinges at the top of the airfoil at both the root and at the mid-span. The invention described here improves upon Schertz in part by folding from the bottom of the airfoil. This results in a more compact design which requires less volume to actuate and that offers superior protection to the hinge in the root of the wing as it is not exposed to the ground.
Other prior methods include wings that combine rotation and folding mechanisms. An example of this style is seen in the concept put forth by Bragg (U.S. Pat. No. 6,086,014). The complicated nature of this combined style necessitates either manual operation or a heavier and more complicated actuation system than is put forth in this invention. Manual operation of the wing folding and unfolding process has proven to be commercially undesirable.
The invention described here improves upon many of the detailed elements of the prior art as well as the basic configuration of the stowed wings. For optimum aerodynamic performance and protection of key mechanisms in both the stowed and deployed configuration, this invention improves upon the fairing panels described by Paez (U.S. Pat. No. 5,372,336) by providing a fair surface in both configurations. Also, instead of adding an additional third rigid component to fair the wing surface only in the deployed configuration, this invention simplifies the fairing by using two panels connected to the fuselage and inboard wing section. The panel fairing technique presented here is an improvement for roadable applications over the elastomeric fairing proposed by Gruensfelder (U.S. Pat. No. 6,076,766) as it provides a more durable and cost-effective method of fairing the surface of the structure.
Any safe folding wing mechanism must also include a method by which the wings are secured in place in both its folded and deployed configurations. In the prior art, this is often accomplished through the use of locking pins. This method is seen in both military and roadable aircraft folding wing mechanisms. See Veile (U.S. Pat. No. 5,558,229) and Spitzer (U.S. Pat. No. 6,082,665) for an example of each. The invention described here is an improvement on previous wing locking techniques as it allows a quick, simple, direct visible and tactile check of the locking mechanism before flight by the pilot to ensure safe operation.
The locking and unlocking mechanisms are activated by the same automated process as the wing folding and deployment, thus eliminating the need for secondary mechanisms. This is an improvement over inventions such as that described by Pham (U.S. Pat. No. 6,129,306) in which a pin is inserted for flight and a bungee cord is required to secure the wings when stowed. By eliminating sliding components in the wing root, the potential for debris to interfere with the folding and locking operation is significantly reduced. The wing locks described in this invention are an improvement over prior art in that they are both safer and more convenient than previous roadable aircraft locking mechanisms while being simpler and lighter weight than military wing locking devices.
In broad terms, when used in the preferred embodiment, the invention presented here represents part of a more elegant and more commercially viable solution to the challenge of folding the wings on a roadable aircraft for ground use than those previously conceived.